ChocoFly 1:3 ASW-17S 7M GPS Racer now in stock in USA

[tewatson]

Completed the wing-side wiring this week. Not going into details since it is pretty straightforward stuff, other than to say all servos are wired separately (no shared power hookups - one wire, one Multiplex connector pin). Using PowerBox premium wire and servo connectors exclusively. I really like their stuff.

The Jeti solder boards for Multiplex green connectors are the shizzle. I no longer dread soldering up these connectors. One piece of advice...when soldering the boards to the connector, make sure you have the opposite side plugged in. The pins "float" a bit in the shell, and having the connector mated holds them in proper alignment.

[lenb]

Tom,
Thank you for taking the time to detail the build. Although the replies to the post are few, the analytics are pretty impressive. There's a good following on this build thread.

Len

[tewatson]

Working on fuse-side wing wiring. Used Emcotec 90 degree solder boards for the Multiplex connectors, to keep the harnesses tight against the fuse right from the connector. These are just a bit trickier than the other boards to arrange and solder, plus the heat shrink procedure required a bit of thought. Came out nice.

[tewatson]

With the harnesses done, time to finish out the pre-molded fuse connector sockets. Standard stuff, though somewhat more time-intensive as there was full-thickness (~2mm) fuse layup material at the bottom of each socket. Drilled and cut to rough size, then finished by hand with small files for a snug fit. Connectors will be held in place with a dab of Goop inside top and bottom, so they can be removed if ever necessary.

[tewatson]

Last night's project was the TEK probe receptacle. With a removable fin/rudder, did not want to monkey with a tail probe, so went with a fuse-mounted setup as used on v-tail ships. The idea is to get it more or less perpendicular to the flight axis, so I fashioned a remedial fuse leveling setup. Taped a straightedge along the airfoil centerline, and used a small carpenter's level on the upper edge to adjust the fuse supports. Shaped a small lite ply block to provide internal support, and with the fuse set level it was easy to see the drilling angle required.

With the 3mm hole drilled in the block and fuse, used the actual probe/receptacle assembly as an alignment guide, and glued the support block inside with thickened five-minute epoxy. Secured the receptacle tube with a small fillet of Goop where it exits the block. Done.

[tewatson]

On to the FES. This part makes me nervous, being my first one and all. There will be three sub-projects - pilot bearing install, motor install, and motor battery placement. Since my plan is to maiden and fly a couple outings just as straight aerotow, don't need to have a functional FES right off the bat. However, the motor does need to be in place since it's obviously a huge factor for balance and will influence where other components need to go (e.g., tow release and flight packs). The motor packs will be at the CG, so the retention system can be figured out later.

Using a Torcman NT530-28 14p/14w motor and Torcman quick-release prop adapter. This will be a 10s setup and the removable prop means quick changeover from powered to straight sailplane. My plan is to set it up with the thrust line centered (zeroed) in pitch and yaw. I interpret this as parallel to the airfoil (pitch) and to the fuse centerline (yaw). Right or wrong, it's what I'm doing.

First step is the motor pilot bearing. Since the motor shaft adapter is a precise fit in the bearing, motor alignment thus follows the bearing. The trick is figuring out not only how to align it, but also to hold alignment while epoxy cures. The motor shaft is 8mm, as is the pilot bearing alignment bushing. Drilled a small hole centered on the nose, and enlarged one drill size at a time, finishing with an 8mm prop reamer. The finished hole size will be 12mm, but left it at 8mm for the bearing install (this is important, as it eliminates the need for an external forward pilot tube support).

Next, set the fuse level. Did this the same way as for the TEK probe install - taped a straightedge along the airfoil centerline, and used a small carpenter's level on the upper edge to adjust the fuse supports.

To actually align the bearing, used a thin-wall 8mm diameter x 1 meter long carbon tube from CST Sales in Tehachapi, CA. It's extremely light (no sagging) and laser-straight. It was a simple matter to pass the tube through the nose hole, slip the bearing and bushing on, then attach a bubble level to the tube. Fashioned a small styrofoam block to sit at the landing gear bulkhead as a rear support, and adjusted the height until the tube showed level (remember, the 8mm nose hole precisely holds the tube up front). The tube is long enough to leave a good portion protruding from the nose, enabling visual yaw alignment. With the tube aligned, applied MGS epoxy mixed with chopped glass and silica to the lower half of the bearing retainer, and slid it forward into place. Re-checked fuse level and tube alignment, then left it to cure.

Because of the fuse profile, a gap remained on the top side of the bearing...enough so even thickened epoxy would sag through. Fashioned a small crescent-shaped filler out of 3mm ply to physically close the gap, using a small diameter brass tube as a holding device to shape and fit it. Once in place, glued the top half of the bearing using the same thickened epoxy mixture. Finally, used the prop reamer to open the nose hole to 12mm.

Explaining all this took longer than actually doing it (excluding cure time, of course). MIL-spec precise? No. Good enough for this application? Yes (I think so, anyway). At least I'm satisfied the thrust line alignment is not off by orders of magnitude. Next up is the motor install.

[jgallacher]

Tom,
Will the fuse stand tall enough with the gear down to clear the prop?

[tewatson]

Yes, it is a two-position gear (will hyper-extend for FES takeoffs).

[tewatson]

The motor install was not as complicated as I had imagined. The oval mounting ring/bulkhead was already a nice close fit around the sides and lower portion, and I filled the top gap with a piece of 3/16" ply attached to the front of the bulkhead, contoured to match the fuse. The objective is to shape the bulkhead such that no twisting or lateral preload force is applied to the pilot bearing. The entire bulkhead perimeter is not accessible with the motor in place...but the motor must be in place to properly position the bulkhead. So, once the dry-fit was good, put the assembly in place and glued it at three different points. When cured, removed the motor and applied the same MGS epoxy mixed with chopped glass and silica all around the bulkhead.

The motor shaft was about 35mm too long, so calculated the correct length and cut it using a Dremel and uber-thin cutoff disc (smaller kerf = quicker cutting). The thin discs are fragile, so care must be taken with alignment once the cut starts getting deep. Working slowly and carefully, the cut took about 40 minutes and I only shattered one cutoff disc.

One nice feature of all this is a plug-in tow leash. Takes just a couple seconds to attach - no more fumbling with hooking a line in the tow release to pull your plane around.

[tewatson]

Tow release next. Used a clever little self-contained unit from Schambeck. It has a split mounting plate arrangement, so to keep it easily serviceable, glued just the lower piece to the fuse with a lite ply platform underneath. Before mounting to the fuse, continued the tow line hole through the platform. With the lower plate epoxied to the fuse, used it as a template with a small drill to outline the hole through the fuse. Final shaping was done by hand with jeweler's files.

Offset the mount slightly to one side for two reasons: Provides additional room for the FES speed controller on the opposite side, and easier to see/manipulate the tow loop without having to stick my head on the ground. YMMV.

[tewatson]

Not much activity - build is paused while I work on a second F5J plane. Contest season is starting up.

[Steve P]

Variety is good!

[tewatson]

No additional work as yet, with other matters soaking up my time. Need to get with it in order to be ready for the Montague GPS event in June.

[tewatson]

Resumed the build recently. Worked out the remaining mechanical items including a rough CG check, which confirmed where things like the flight packs go and allowed me to finalize the cockpit arrangements...more on those things later. Been slowly ticking off the remaining punch-list items, and today's project was graphics.

Used Rapid-Tac application fluid to float the vinyl into position and a felt-edged squeegee to finish. The fluid also helps with adhesion which is nice when working with tight curves.

[tewatson]

After getting some time on the airframe, it became evident the stab throws were too high, even with the servo travel dialed way, way back. Long story short...the stock IDS servo horns are molded resin and an extremely tight fit on the servo splines, so the horns had to be pressed on the servo before mounting in the frame. This also meant the horn had to be long enough so the IDS link pin cleared the servo case. Longer horns = less servo travel and less precision.

Enter custom aluminum IDS horns. Chocofly offers these in three different lengths, and the 3.5mm moment arm size is perfect for the stab. They are a smooth, easy press-fit on the servo splines, which means the linkage arm, horn and pin can be assembled in the frame, and the servo slipped in as a last step. This also means the horn pin no longer needs to protrude above the servo case.

These allowed me to almost double the servo travel while still reducing overall stab throw. Win.

[Scalesoaring]

These metal IDS Arms are in stock in California. They 25-tooth spline so fit FOX (ChocoFly), Futaba, and others. $8.00 each.

email: ohmktg413@gmail.com

Bruce DeVisser

[tewatson]

Finally got the ballast set arranged. Wings are supplied with 18mm diameter tubes, approximately 46.5cm long. Procured brass and tungsten rods, plus PTFE rod for spacers. This allows adding 1-3kg. From top to bottom (weights are total, for both sides):

Spacer + brass = 1kg
Spacer + tungsten = 2kg
Brass + tungsten = 3kg